The OAI2LOD Server Exposing OAI-PMH Metadata as Linked Data - - PowerPoint PPT Presentation

The OAI2LOD Server

Exposing OAI-PMH Metadata as Linked Data

Motivation

• more than 1700 institutions worldwide expose

metadata via the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH) using open standards like URI, HTTP , XML

Motivation

• from 900 investigated OAI-PMH repositories
• avg. number of Items/Data Provider: ~14,000

10 100 1000 1

• 2

, 2 ,

• 4

, 4 ,

• 6

, 6 ,

• 8

, 8 ,

• 1

, > 1 , 24 4 7 16 21 843

Number of items in repository Number of repositories

Goal

Library of Congress Austrian National Library

• Bib. Uni.

De La Sabana BioMed Central Caltech Digital Libray DSpace @

• Inst. X

Fedora @ Inst. Y DBPedia

OAI-PMH at a glance

Item

• identifier: URI

Record MetadataFormat

• metadataPrefix: String

Set

• setSpec: String

1 1..* * 1 0..* 0..*

OAI-PMH at a glance

sample request:

http://memory.loc.gov/cgi-bin/oai2_0? verb=GetRecord& identifier=oai:lcoa1.loc.gov:loc.gdc/gcfr.0018_0163& metadataPrefix=oai_dc

OAI-PMH at a glance

sample response:

<OAI-PMH...> ... <header> <identifier>oai:lcoa1.loc.gov:loc.gdc/gcfr.0018_0163</identifier> <setSpec>ascfrbib</setSpec> </header> <metadata> <dc:title>Don Christopher Columbus to his friend, Don Louis de Santangel</dc:title> <dc:creator>Columbus, Christopher</dc:creator> ... </metadata> </GetRecord>

OAI-PMH at a glance

• ListRecords
• batch retrieval of records
• ListIdentifiers
• returns item identifiers
• ListSets
• returns available sets
• Identify

The OAI2LOD Server

• makes OAI-PMH resources (items/sets)

dereferencable via their URIs

• provides metadata access for humans and

machines that “do not know” the OAI-PMH protocol

• exposes a SPARQL interface to these data
• links metadata with other LOD sources

The OAI2LOD Server

OAI2LOD Server OAI-PMH Data Provider HTTP Config & XSL HTML Browser Linked Data Clients SPARQL Clients Request Handler / Dispatcher Triple Store OAI-PMH Harvester HTTP

The OAI2LOD Server

• LOD Rule 1+2 - “Things should have (resolvable)

URIs”

• Items: http://example.com/resources/item/
• ai:lcoa1.loc.gov:loc.gdc/gcfr.0018_0163
• Sets: http://example.com/resources/set/

ascfrbib

• Vocabularies

The OAI2LOD Server

• LOD Rule 3: “Deliver useful information when

URIs are dereferenced”

• Content negotiation based on HTTP Accept
• RDF for machines
• (X)HTML for humans

The OAI2LOD Server

• LOD Rule 4: “Metadata should contain links to
• ther related resources”
• link to any other OAI2LOD / LOD data sources
• configurable linking property - e.g., rdfs:seeAlso
• linking heuristics based on configurable string

similarity metrics (e.g., Levensthein, SoundEx)

Outlook

• the number of OAI-PMH repositories will grow
• major initiatives push its adoption
• e.g., “The European Library”
• integrates 47 national libraries
• provides access to approx. 150 M items

Outlook

• OAI-ORE (Object Reuse and Exchange)
• latest standardization effort for the

“description and exchange of aggregations of Web resources”

• data model is based on RDF
• concepts have dereferencable URI identifier
• aggregations are the means to “link” resources

Further Infos

• OAI2LOD - Demos, Download & Instructions:

http://www.mediaspaces.info/tools/oai2lod/

• Contact

bernhard.haslhofer@univie.ac.at

• the end -

BACKUP

Motivation

• each OAI-PMH

compliant repository

• MUST expose Dublin

Core metadata

• MAY provide other

MetadataFormats

Unqualified Dublin Core RFC1807 OAI MARC MARC21 Slim METS ETDMS UK ETD DC MPEG-21 DIDL ? 300 600 900 39 41 45 52 69 94 108 110 900

Top 10 Metadata Standards